Biology ch 13

• without sex
• single organism productes genetically identical offspring
• two sexes not necessary for reproduction
• ONLY MITOSIS IS EXHIBITED
• THERE IS NO SPERM
• TO FERTILIZE AN OVUM
• DAUGHTER CELL IS IDENTICAL TO PARENT CELL IN GENETICS

• 1. Binary Fission
• 2. Budding
• 3. Fragmentation
• 4. Parthenogenesis

• Bacteria (prokariotic cell)
• cell splits into two identical cells
• Genetically Identical
• Takes 20 minutes for bacteria to reproduce

• EUKARYOTE (Aquatic organisms - Hydra, sponges)
• GENETICALLY IDENTICAL
• Sessile - fixed - used by organisma that are fixed to one spot and cant move
• Buds a new organism off the side and pinches it off

• Worms
• Genetically Identical
• Worm splits into 7 to 9 pieces

• "VIRGIN BIRTH"
• Females give birth to females
• Whip tailed lizard - no males in species- lay eggs - only daughters
• Honey Bee - Queen mates one time in life - sperm receptical to make drones
• Drones - males - sit around
• Worker bees - female - no sperm used - genetically identical

• sometimes considered asexual
• Planaria - starfish
• *when injured* body splits and forms two identical organisms

• organism contains both male and female sexual organs
• can produce both eggs and sperm

• The divistion of the nucleus of a cell
• Only occurs in somatic cells
• Results in two Genetically Identical cells
• Causes of mitosis:
• Death
• Damage
• Disease
• Growth
• Results In:
• 1 Replication
• 1 Division

all body cells except the reproductive cells

• chromosomes when they are unpacked in the nucleus of the cell.
• cannot see individual chromosomes in this state
• when DNA is getting ready to replicate it packs up its chromosons and condendes into recognizable strands

• DNA duplicates itself - results in two identical chromotids attached as the centromere
• centromere - "waist" where two chromotids are attached
• arm - part of the chromotid on either side of the centromere
• 

• includes mitosis and cytokinesis
• shortest part of cell cycle
• alternates with interphase

• 90% of cell cycle
• cell grows and copies its chromosomes in prep for cell division
• G₁ Phase - first gap - cell grows
• S Phase - synthesis - copies its chromosomes
• G₂ Phase - second gap - grows more - produces more cytoplasm and organelles

• 1. Prophase
• Prometaphase (lab)
• 2. Metaphase
• 3. Anaphase
• 4. Telophase
• 5. Cytokinesis
• 

• each of the sister chromatids has a kinetochore - a protein
• the two kinetochores face in opposide directions
• during metaphase - microtubules attached to the centromere at the kinetochore and pull the sister chromatids apart

• the nuclear membrane breaks down
• each duplicates chromosome appears as two sister chromatids, bound at a point called the centromere, making an "X" shape
• centrioles duplicate form and move toward the poles (in an animal cell)
• mitotic spindle begins to form
• 

• Nuclear membrane is gone
• Cenrtosomes are at the poles producing microtubules (Mitotic spindle) which attached to the kinetochore of each chromotid
• The chromosomes are lined up along the cell's equator, (the equatorial plate)
• When the individual chromatids (½ of the"X") are separated from the chromosome (the "X"), they are now each referred to as a chromosome (i.e. In metaphase, the chromosome, composed of two chromatids, separates into the individual chromatids, which are then renamed chromosomes, even though they were only one half of a chromosome only moments before!)
• 

• Microtubules pull sister chromotids apart - now called Daughter Chromosomes
• This stage is almost egg-shaped because of the pulling of the microtubules attached to the kinetochore (a protein) of the centromere.

• mitosis (spliting of one nucleus into two) is now complete
• nuclear envelope reforms
• cleavage furrow
• 

• cytoplasm divides and in animal cells the cleavage furrow pinches the cell in two
• you now have two diploid cells

diploid - notated as 2n - contains two sets of chromosomes - one inherited from each parent (for humans 2n = 46 (has 22 homologs and 1 set of sex chromosomes)

haploid - notated as n - contains one set of chromosomes - for humans n = 23 - 22 autosomes and 1 sex chromosome

• two chromosomes composting a pair have the same length, centermere position, and pattern
• both chromosomes of each pair contain genes controlling the same inherited trais (on trait from mom and one from dad)
• Humans have 22 pair of homologs (44 chromosomes) and one set of sex chromosomes (female XX is a homolgous pair but make XY do not match)

• sex cells - eggs and sperm (haploid cells)
• zygote is a fertilized egg (becomes diploid because it contains two sets of chromosomes)

• One cell results in 4 that are not genetically identical
• Process:
• 1 Replication
• 2 Divisions
• 

• Prophase I
• Metaphase I
• Anaphase I
• Telophase I
• Cytokinesis I
• Prophase II
• Metaphase II
• Anaphase II
• Telophase II
• Cytokinesis II

• In interphase the chromosomes replicated forming sister chromotids
• Homologues pair up - (sister chromotids that control same traits pair up - one set for maternal genetic materical and one for paternal
• Form a Tetrad (4 chromosomes)
• Crossing Over - exchange corresponing segments of DNA by nonsister chromotids
• 1st step in genetic variation - crossing over
• Chiasmata - points where crossing over occured
• Centrisomes move to poles, spindle forms, nuclear envelope breaks down
• 

• 2nd step in genetic variation - homologs can line up along the metaphase plate in any order
• both chromotis of one homologue are attached to the kinetochore mcrotubules from one pole
• 

• Each pair of homologous chromosomes separates and are pulled toward the poles
• Sister chromotids stay together as they are pulled to the pole
• Starts to get egg shaped
• 

• Two haploid cells form (each cell has a single set of replacated chromosomes)
• each chromosome consisted of two sister chromotids that have exchanged DNA with their non sister homologue
• animal = cleavage furrow forms
• plant = cell plate forms
• 

• cells pinch off
• results in two haploid cells ( one set of chromosomes) with a set of sister chromotids in each cell

• starts with two haploid cell with sister chromotids in each cell that are not genetically identical
• No crossing over
• Spindle forms, centrisomes move to poles

• chromosomes line up along the metaphase plate (equator)
• kinetochore of sister chromotids are attached to poles
• 

• two haploid cells with non-identical sister chromotids
• sister chromotids (which are not genetically identical due to crossing over) are pulled apart and pulled toward the poles
• 

• Nucleus forms
• Animal - cleavage furrow

• cytoplasm separates
• resuls in :
• 4 haploid daughter cells (one set of chromosomes)
• Each of the daughter cells is genetically different form the other sister cells and from the parent cells
•